To perform various operations such as vehicle door unlocking and locking, a remote keyless entry system or a smart entry system has been applied widely. In such a remote keyless entry system, a user transmits electric waves having predetermined code information from a transmitter held by the user toward a receiver attached to a vehicle. The receiver receives the electric waves and a controller mounted on the vehicle performs vehicle door unlocking and locking operations when previously stored code information meets the predetermined code information.
Some of the receivers of this type have an antenna coil capable of receiving electric waves in three axial directions. As a conventional art relating to antenna coils capable of receiving such electric waves in three axial directions, there is, for example, a structure disclosed in Patent Document 1.
Patent Document 1 discloses that a coil structured in a cross shape is received in a case having a coil receiving portion of a square shape. The structure disclosed herein is made so that the extending directions of respective coil portions intersecting in a cross shape are positioned in parallel to respective sides of the coil receiving portion.    Patent Document 1: WO2005/088767 (refer to FIGS. 1, 5, and 6 and others)